HFSS & HFSS & ePhysicsePhysics Features for the Simulation Features for the Simulation of Microwave Power Applicationsof Microwave Power Applications

Bogdan C. Ionescu

Brad Brim

Ansoft Corporation

HFSS Applications

Microwave

Antennas& Arrays PCBs

Packaging

ICs

HFSS

The Ansoft DesktopHFSS is a “design environment” enablingan automated 3D EM-based design flow

design flow management with a familiar use modelparametric design database creation and editingparametric data management and access

An HFSS Design Example

High Power HF Components

Pass band iris filter

Trend: Eliminate Boundaries

System Design

Circuit DesignTransient & Frequency

Domain

FEA Based Component DesignElectromagnetics, Thermal, Mechanical

Model Extraction

Co-Simulation

Model Extraction

Co-Simulation

Model Order Reduction

-50

-40

-30

-20

-10

0

0 5 10 15 20Frequency (GHz)

S M

atrix

(dB

)

S11 (fast sweep)

S11 (interp. sweep)

Three layers:L1: 10mm, εr=9.8L2: 10mm, εr=2.1, tanδ=0.001L3: infinity, εr=1

WideBandwidth

-50

-40

-30

-20

-10

0

5 10 15 20Frequency (GHz)

S M

atrix

(dB

)

S11 (fast sweep)

S11 (interp. sweep)

Wide ABCBandwidth

Fast Frequency Sweep

B. Anderson, J. E. Bracken, J. B. Manges, G. Peng and Z. J. Cendes, ”Full-Wave analysis in SPICE via Model-Order Reduction”, IEEE Transactions on Microwave Theory and Techniques, Vol. 52, No. 9, pp. 2314-2320, September 2004.

Dynamic Link

ePhysics for Electromagnetic Applications

HFSSEM high frequency

MaxwellEM low frequency

Electrostatic

Magnetostatic Electric

ePhysics:- Thermal- Stress- CFD- ….

Higher Level AnalysisGeometry

Maxwell(low frequency)

HFSS(high frequency)

ePhysics:Thermal/StressOptimetrics:

Parametrics/Optimization/Sensitivity Analysis

CAD Level

Electro-magnetics

Level

Multi-physicsLevel

ePhysics TM Functional LinksHFSS

Magnetostatic+ DC Conduction

Eddy Current

Static Thermal

Transient EM+Rigid Body Motion

Transient Thermal

Electrostatic

Elastostatic

Static Thermal

Transient Thermal

Elastostatic

Thermal Transient SolutionGeometry (. sm3 from HFSS, use File/Open rather than File/Import)

Material properties (thermal conductivity, specific heat, mass density)

Sources (volumetric power loss density, superficial power loss density, other non-electromagnetic sources)

Boundary conditions (prescribed temperature, convection, radiation)

Solver setup (time step, HFSS mesh, thermal mesh mapping)

IN:From HFSS

From ePhysics

Temperature distribution (scalar)Heat Flow (vector)Executive parameters (average temp., hot spot temp., cold spot temp., locations)Post processing macro results

OUT:

ALL mesh filesare necessary!

1

2,3

4

Static Stress Solution(coupled with thermal transient)

Geometry (already there, with origin in . sm3 from HFSS)

Material properties (Young’s modulus, Poisson’s ratio,

coefficient of thermal expansion)

Sources (temperature distribution, other non-thermal

sources)

Boundary conditions (displacement)

Solver setup (mesh, mapping)

IN:

Displacement (vector)Traction (vector)Von Mises stress (vector)Executive parameters (max von Misesstress, max principal stress, etc.)

OUT: (at user-selected time steps)

3D Thermal Transient

( ),t vc q Q t xρ ϑ∂ − ⋅= ∇ +r r

q ϑ= − ∇kr

( ) ( )00, x xϑ ϑ=r r

( ) ( ) ( )ˆ C rq n q hϑ ϑ ϑ ϑ⋅ = = −r

Dϑ ϑ=

initial condition

vQ E J= ⋅r r

Solution Process HFSS - Thermal

HFSS Thermal

Adaptive Refinement

Loss Mapping

Initial (coarse)thermal mesh

Controls bothaccuracy of thermalsolution AND accuracyof power loss mapping

Heat Transfer MechanismsConduction Convection Radiation

Natural

Forced

Convection Mechanism on a Vertical Wall

h = h(Pr, Gr)convection coefficient

depends on the temperatureof the wall

Boundary layerTf = (Tw + Tamb)/2

TwTamb

Frequently Used ThermalSources

On solids

On surfaces,surface can bebetween objects

Frequently Used Thermal Boundary Conditions

Can be functional!(temperature – dependent)

Can include radiation if needed!

Ferrite Circulator Application-geometry-

Port size:1” by 0.5”

1.7 “

0.3”

Power flowFrequency: 10 GHzOperating power: 1 KW

Ferrite component

Wave guide

Ferrite Circulator Application-materials-Ferrite

Silver

Air

Note: specify zerothermal conductivity to exclude object fromthermal simulation;zero Young’s modulusto exclude it from stress simulation.

Ferrite Circulator Application-thermal boundary conditions-

4 vertical faces(2 shown + 2 symmetricon the other side)

2 horizontal facesfacing “up”

2 horizontal facesfacing “down”

3 side facesof ferritecomponent

convective & radiative boundary conditions

Ferrite Circulator Application-stress boundary condition-

bottom of circulatorconstrained with homogenous

displacement condition

Note: ferrite blockis touching at both ends the wave guide

Ferrite Circulator Application-HFSS sources-

Loss

time

simulationtime

Use Write commandin HFSS post processor

after scaling to actual power

(Creating time dependent thermal loads)

Model/Functions…Menu Button

1. Define dataset and save

2. Create & add function (load)

3. Enter load name as value

4. Assign to solid

Thermal Static Solution Setup

Temperature everywhere in thethermal model at t =0

Field initial condition = non-uniformtemperature distribution

Used in transient thermal mesh generation:

(instructs the adaptive process to considerthe combination of sources at specified time)

Thermal Transient & Stress Solution Setup

Thermal transient setup

Stress setup

Ferrite Circulator Application-thermal results, field-

Temperature distribution att = 1,200 s

Power

Power

Power

Heat flow distributionat t = 1,200 s

Ferrite Circulator Application-thermal results, exec param-

Ferrite Circulator Application-stress results-

Deformation plots

magnitude

vector Scaled deformation

Ferrite Circulator Application-stress results-

Von Mises stress

Vector displacement

Y component of vector displacement

Ferrite Circulator Application-what ifs!?… and whys?-

Model with 25 um air gapbetween ferrite and wave guide

Displacement plots

Global: steady state temperature T = 71.4 C(previous temperature T’ = 64.4 C)

Von Mises stress

Ferrite Circulator Application-what ifs!?… and whys?-

Model is kept at -50 oC,no air gap above the ferrite

Von Mises stressVector displacement

Scaled deformation

Chebyshev Filter Application-model data-

286

126

18

10

Central frequency for thermal analysis: 400 MHzInput power: 200 W

Chebyshev Filter Application-materials-

Aluminum: for rods & housingNon-structural aluminum: rest of the metallicobjects (to exclude them from stress analysisbut not from thermal analysis)

“Non_structural” aluminum:

Chebyshev Filter Application-boundary conditions-

Thermal boundaries

Convective & radiativeboundary condition

Symmetry plane:leave unconstrained =

= thermal flux tangent = = adiabatic boundary

Stress boundary

Zero X, Y, Z displacementon top face

Chebyshev Filter Application-results-

Magnitude of displacement

Temperature distributionScaled deformation

Displacement vector

High Power HF Components

High Power Handling HF (760 MHz) filters

Input

Output

Outer body temperature distribution

Tune-up pins

760 MHz Filter, High Power Input(KW range)

Surface current densitydistribution calculated by HFSS

Average temperature of mid-plate

Temperature distribution at t = 1000 s

Microtech Model

Air velocity = 76 m/s

Wave guide

Temperature profile in a planecontaining the “hot spot”

Average heat-sink temperature

Very good match with experimental data!

Microtech Model

Procedure to calculate forced convection coefficient

νLu ⋅

=Re

58.0333.0

5333.05.0

105Re)871Re037.0(Pr105RePrRe664.0

⋅≥−⋅⋅=

⋅≤⋅⋅=

ifNuifNu

-Calculate specific CFD numbers:- Reynolds number - Nusselt number

- Calculate convection coefficient LNuH σ⋅

=

Fluid velocity

Laminar flow

Mixed flow

IC structure in HF incident field

Metal ground planes & viasimbedded in ceramic block

Top plane heated by incident wave

Temperature distributionon ceramic block after 200 s

Temperature distributionon cross section

Microwave HeatingIndustrial Size Applicator

Waveguide

Mineral ore

915 MHz,20 KW

The Benefits of HFSS &ePhysicsHFSS provides an environment for3D EM-based design flow automation

Virtual Prototyping reduces engineering time, speeds time to market

HFSS uniquely provides assured accuracy for a broad set of applications to complement the highest level of automationEvaluate thermal and stress consequences of electromagnetic fields with ePhysics

Import Geometry

Draw Parameterized Geometry

Perform Analysisand Optimization

Plot Results

Examine Fields

Export Results

Define Materials,Boundaries, Ports

Setup Analysisand Optimization

automated loop

Simulate thermal

Simulate stress

ePhysics